4–20 mA Wiring for Controllers
Application Guide
Contents
KMC Controllers and 4–20 mA Inputs/Outputs..................................1
Input Wiring................................................................................2
Output Wiring..............................................................................3
Troubleshooting..........................................................................4
Accessories................................................................................4
Important Notices........................................................................4
Support......................................................................................4
KMC Controllers and 4–20 mA Inputs/Outputs
KMC Conquest controllers, the BAC-A1616BC Building Controller, and the KMD5220 (input module for the LAN Controller) can natively read a 4–20 mA signal
on their input terminals (after proper configuration via a jumper or software).
Older KMC controllers require an external 250 ohm (or more readily available
249 ohm) resistor wired across the input and ground terminals. (See
Accessories on page 4.) The resistor converts the mA signal into a voltage
signal that the controller can recognize. The controller’s physical input is
then set (via jumpers or switches) for an active voltage sensor, and software
configures the internal functioning for 4-20 mA. (See the controller’s installation
guide and software help information.)
The external 250 ohm resistor shown in Input Wiring on page 2 are to be
used with the following controllers:
• FlexStats*
• BAC-58xx and KMD-58xx
• BAC-7xxx and KMD-7xxx
• Older KMDigital controllers
*NOTE: To ensure accurate readings from the internal temperature sensor of a
FlexStat, do not mount the 250 ohm resistor inside the FlexStat’s case.
To get a 4–20 mA output from a (compatible) KMC controller, use an HPO-6704
output override board. Alternately, an REE-2005 voltage-to-current converter
module can convert a 0–10 VDC output signal from any controller into a 0–20
mA output signal. See Output Wiring on page 3 and Accessories on page
4.
KMC Controls, 19476 Industrial Drive, New Paris, IN 46553 / 877-444-5622 / Fax: 574-831-5252 / www.kmccontrols.com
Input Wiring
*NOTE: A resistor is internally supplied with newer KMC controllers (see KMC
Controllers and 4–20 mA Inputs/Outputs on page 1). An external
resistor must be supplied for other controllers (see Accessories on
page 4).
Signal –
Input
GND
* 250 Ohms
Signal +
4–20 mA
Transmitter
+ –
Regulated VDC
Power Supply
Controller
Illustration: Two-Wire Loop Powered
Signal
Input
GND
* 250 Ohms
–
+
4–20 mA
Transmitter
+ –
Regulated VDC
Power Supply
Controller
Illustration: Three-Wire Loop Powered
Signal +
Input
GND
* 250 Ohms
Signal –
Power –
Power +
4–20 mA
Transmitter
+ –
Regulated VDC
Power Supply
Controller
Illustration: Four-Wire Loop Powered
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Output Wiring
For a 4–20 mA output from a (compatible) KMC controller, use an HPO-6704
output override board in the provided slot for the output. The HPO-6704 converts
a 0–10 VDC output signal in the controller to a 4–20 mA output. Compatible
controllers include:
• BAC-A1616BC
• BAC-59xx
• BAC-58xx and KMD-58xx
• KMD-52xx
NOTE: The controller and HPO-6704 board supply the power to the 4–20 mA
output circuit. No external regulated power supply is used in that circuit.
See Illustration: HPO-6704 Installed in Compatible KMC Controller on
page 3.
Output
GND
+ 4–20 mA
– Device
HPO-6704 (Installed
in Override Board
Slot for Output)
Controller
Illustration: HPO-6704 Installed in Compatible KMC Controller
Alternately, an REE-2005 voltage-to-current converter module can convert a
0–10 VDC output signal from any controller into a 0–20 mA output.
NOTE: The REE-2005 supplies the power to the 4–20 mA output circuit. No
external regulated power supply is used in that circuit. See Illustration:
HPO-6704 Installed in Compatible KMC Controller on page 3.
24 VAC or
22–40 VDC
~/+
–
GND
0–10 VDC Output
+ 4–20 mA
– Device
Controller
Illustration: REE-2005 Used with Other KMC Controller
For more information about installation and usage of these accessories, see
the accessory documentation as well as the installation guide for the respective
controller.
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Troubleshooting
• Check the wiring.
• Check controller configuration.
• For an HPO-6704, ensure board is in the slot corresponding to the output
terminals.
• Check the sensor and power supply.
Accessories
HPO-0069
249 ohm resistors, pack of 100
HPO-6704
4–20 mA output override board with
adjustable override potentiometer,
HAO switch, and LED indicator
REE-2005
Voltage-to-current transducer module, 0–10 VDC to 0–20 mA
Important Notices
The KMC logo and KMC Controls are registered trademarks of KMC Controls,
Inc. Other products and name brands mentioned may be trademarks of their
respective companies or organizations.
All rights reserved. No part of this publication may be reproduced, transmitted,
transcribed, stored in a retrieval system, or translated into any language in any
form by any means without the written permission of KMC Controls, Inc.
The material in this document is for information purposes only. The contents
and the product it describes are subject to change without notice. KMC
Controls, Inc. makes no representations or warranties with respect to this
document. In no event shall KMC Controls, Inc. be liable for any damages, direct
or incidental, arising out of or related to the use of this document.
Support
Additional resources for product specifications, installation, configuration,
application, operation, programming, upgrading and much more are available on
the KMC Controls web site (www.kmccontrols.com). To see all available files,
log-in to the KMC Partners site.
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© 2015 KMC Controls, Inc.
Specifications and design subject to change without notice
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